Structure body for use in friction stir welding

ABSTRACT

An abutted portion of face plates  12   b  and  22   b  of hollow frame members  10  and  20  is carried out according to a friction stir joining. Next, a connection member  30  is mounted, one end of the connection member  30  is abutted to an end portion of the face plate  11  of the hollow frame member  10 . Under this condition, the abutted portion between the face plate  11  and the connection member  30  is carried out according to the friction stir joining. An overlapping portion between another end of the connection member  30  and the hollow frame member  20  is carried out according to the friction stir joining. According to demands, the connection member  30  and the face plate  21  of the hollow member  20  is welded. Without of regard of a dimension accuracy of the hollow frame member and the like, a good joining from one side face of the hollow frame member can be carried out.

This application is a Divisional application of application Ser. No.09/637,020, filed Aug. 14, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a friction stir joining method, astructure body manufactured according to a friction stir joining method,a hollow frame member carried out a friction stir joining method, and aconnection member for a hollow frame member carried out a friction stirjoining method.

For example, the present invention is suitable for a friction stirjoining method, a structure body manufactured according to a frictionstir joining method of an aluminum alloy made extruded frame memberwhich is used in a railway vehicle or a building structure and the like,a hollow frame member carried out a friction stir joining method, and aconnection member body for a hollow frame member carried out a frictionstir joining method.

A friction stir joining method is a method in which by rotating a roundrod (it is called as “a rotary tool”) which is inserted into a joiningportion and moving the rotary tool along to a joining line of extrudedframe members, and the joining portion is heated, softened andplastically fluidized and solid-stately joined.

The rotary tool is comprised of a small diameter portion which isinserted into the joining portion and a large diameter portion which ispositioned at an outside portion of the small diameter portion of therotary tool. The small diameter portion of the rotary tool and the largediameter portion of the rotary tool have the same axis. A boundarybetween the small diameter portion of the rotary tool and the largediameter portion of the rotary tool is inserted a little into thejoining portion. The above stated technique is disclosed, for example inJapanese application patent laid-open publication No. Hei 9-309164 (EP0797043 A2).

In FIG. 9 of this document of Japanese application patent laid-openpublication No. Hei 9-309164 (EP 0797043 A2), a joining of two faces ofthe hollow extruded frame members is carried out from one face of thetwo faces of the hollow extruded frame member. Namely, a plate of oneside face is abutted and from another face side of the another plate afriction stir joining is carried out. An outer face side of the plate isjoined flatly. An end portion of the plate of the another face side isorthogonal to a thickness direction.

As shown in FIG. 9 of the above stated document of Japanese applicationpatent laid-open publication No. Hei 9-309164 (EP 0797043 A2), a casewhere a hollow frame member is carried out from a face of one sideaccording to the friction stir joining. In this case, it is importantthat an interval of plates 33 and 33 of upper faces of two hollow framemembers 31 and 32 and an accuracy of a width of a coupling member 60which is arranged this portion.

Both ends of the coupling member 60 are abutted to the plates 33 and 33and are joined. For this reason, when the interval of the upper faceplates 33 and 33 is smaller than a width of the coupling member 60, itis impossible to arrange the coupling member 60.

In reversibly, when the interval of the upper face plates 33 and 33 islarger than the width of the coupling member 60, it is difficult tocarry out the friction stir joining to the abutted portion. Namely, itis important that a gap of the abutted portion formed between the plate33 and the coupling member 60 is small.

However, in accordance with a manufacturing tolerance during a press-outprocessing of the hollow frame members 31 and 32 and the coupling member60 and a manufacturing tolerance during the friction stir joining, tothe abutted portion a large gap can occur easily. In a case of thejoining of the car body of the railway vehicle, the above large gap isremarkable in the case in which many hollow frame members are joined byputting them side by side.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a friction stir joiningmethod, a structure body manufactured according to a friction stirjoining of an aluminum alloy made extruded frame member which is used ina railway vehicle or a building structure and the like, a hollow framemember carried out a friction stir joining method, and a connectionmember body for a hollow frame member carried out a friction stirjoining method in which regardless of a dimension accuracy of a hollowframe member and the like, a good joining of the hollow frame member iscarried out from a face of one side thereof.

The above stated object can be attained by in case where one of faceplates of a hollow frame member is joined using a connection member, oneend of the connection member is carried out according to an abuttingjoining and another end thereof is carried out according to anoverlapping joining.

The above stated object can be attained by a friction stir joiningmethod wherein preparing two hollow frame members in which between twosheet face plates is connected according to plural ribs, and an endportion of one of the two face plates is projected from an end portionof another of the two face plates, joining the projected face platestogether with from a side of the another of the two face platesaccording to a friction stir joining, arranging a respective endportions of one connection member to a connection portion between theend portion of the another of the two face plates of the one of the twohollow frame members and a connection portion between the end portion ofthe another of the two face plates of the another of the two hollowframe members and the ribs, and carrying out the friction stir joiningto an abutted portion between the one of the two hollow frame membersand one end of the connection member, and carrying out an overlappingportion between the another of the two hollow frame members and anotherend of the connection member according to the friction stir joining froman outer side of the two hollow frame members.

The above stated object is attained by a structure body wherein, twohollow frame members are joined, in the respective two hollow framemembers, between two sheet face plates is connected according to pluralribs, and an end portion of one of the two face plates is projected froman end portion of another of the two face plates, the projected faceplates are carried out together with according to a friction stirjoining, a respective end portions of one connection member is carriedout the friction stir joining to a connection portion between the endportion of the another of the two face plates of the one of the twohollow frame members and a connection portion between the end portion ofthe another of the two face plates of the another of the hollow framemembers and the ribs, the joining between the one of the two hollowframe members and one end of the connection member is joined to anabutted portion of the two hollow frame members and the connectionmember, and the joining between the another of the hollow frame membersand another end of the connection member is joined to an overlappingportion of the two hollow frame members and the connection member.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a longitudinal cross-sectional view showing a joining portionbefore a joining of a structure body of one embodiment according to thepresent invention;

FIG. 2 is a longitudinal cross-sectional view showing a joining portionafter a joining of a structure body one embodiment according to thepresent invention;

FIG. 3 is a longitudinal cross-sectional view showing a joining portionof a hollow frame member of a structure body of one embodiment accordingto the present invention;

FIG. 4 is a perspective view showing a car body of a railway vehicle;

FIG. 5A is a longitudinal cross-sectional view showing a joining portionof a structure body another embodiment according to the presentinvention; and

FIG. 5B is a longitudinal cross-sectional view showing a joining portionof a structure body another embodiment according to the presentinvention.

DESCRIPTION OF THE INVENTION

One embodiment of a friction stir joining method, a structure bodymanufactured according to a friction stir joining method, a hollow framemember carried out a friction stir joining method, and a connectionmember for a hollow frame member carried out a friction stir joiningmethod according to the present invention will be explained from FIG. 1to FIG. 4.

FIG. 1 is an enlarged view showing an essential portion of a sidestructure body of a railway vehicle of FIG. 3. FIG. 3 is a longitudinalcross-sectional view showing a side structure body of a structure bodyof FIG. 4.

A car body 200 of a railway vehicle is comprised of a side structurebody 201 for constituting a side face, a roof structure body 202 forconstituting a roof, a stand frame 203 for constituting a floor, and aside structure body 204 for constituting an longitudinal direction endportion.

Each of the side structure body 201, the roof structure body 202, andthe stand frame 203 is constituted respectively by joining pluralextruded frame members. A longitudinal direction of the extruded framemember is formed toward a longitudinal direction of the car body. Theextruded frame member is a hollow frame member made of an aluminumalloy.

A constitution and a joining method of a hollow extruded frame members10 and 20 for constituting the side structure body 201 will beexplained. Other portions and other structure bodies are similar to theabove.

The hollow frame members 10 and 20 are comprised of two sheet faceplates 11, 12 and 21, 22 and truss shape structure arranged plural ribs13 and 23. The two sheet face plates 11 and 12 are substantially inparallel. The two sheet face plates 21 and 22 are substantially inparallel.

A pitch of the truss structure according to the ribs 13 and 23 is thesame. The truss structure is constituted by the ribs 13 and 23 and acenter line of a plate thickness of the respective face plates 11, 12and 21, 22. An apex is formed at a side of the face plates 11, 12 and21, 22.

At a vicinity of the apex of the truss structure in an inner side of thevehicle, rails 19 and 29 for installing machines and apparatuses areprovided integrally. The rails 19 and 29 are comprised of L shape twomembers. The rails 19 and 29 become seats for installing the machinesand apparatuses such as interior mounting plates and chairs and thelike.

End portions of the face plates 12 and 22 which are positioned an outerface side of the car body project to a side of the adjacent hollow framemembers 20 and 10 from the end portions of the face plates 11 and 21 inthe inner side of the car of the railway vehicle. These projected faceplates are indicated by 12 b and 22 b.

By abutting end portions of the face plates 12 b and 22 b to each other,the friction stir joining is carried out. A plate thickness of each ofthe face plates 12 b and 22 b is thicker than another portion of theface plates 12 and 22.

The hollow frame members 10 and 20 are mounted on a bed 240 by layingthe face plates 12 and 22 at the lower portion. The side of the faceplates 11 and 21 are formed to the upper portion. By inserting a rotarytool 250 to the joining portion from the upper portion and the frictionstir joining is carried out. The friction stir joining is carried outfrom the inner side of the car of the railway vehicle.

To the end portion (the abutted portion) of the face plates 12 b and 22b, raised portions 16 and 26 which project in the inner side of the car(namely, the face plates 11 and 21 side) are provided. A width and aheight of each of the raised portions 16 and 26 are substantially thesame.

Between the end portion of the face plate 11 in the inner side of thecar and the end portion of the face plate 21 is joined with a connectedthrough a connection member 30. To the end portion of the connectionmember 30 is mounted or overlapped to the seats 17 and 27 which areprovided on the apex of the truss structure.

The seat 17 is formed at the end portion of the hollow frame member 10from a normal line which passes through an intersecting point betweenthe rib 13A and the rib 13B. A face reaching from the seat 17 to theouter face (the upper face) of the face plate 11 is formed on the abovestated normal line. To an end portion of the face plate 11 at the seat17 side, a raised portion 11 b which projects to the outer face (theupper face) side is arranged.

The end portion of the connection member 30 a raised portion 32 whichprojects to the outer face (the upper face) side is arranged. A widthand a height of the raised portions 11 b and 32 are the same to those ofthe raised portions 16 and 26. The width of the seat 17 is the same tothe width of the raised portion 32.

The seat 27 is arranged at an intersecting point between the ribs 23Aand the rib 23B as a center. At a center of the width of the seat 27 theabove stated intersecting point is arranged. Namely, the apex of thetruss structure of the end portion is arranged at a central portion ofthe width of the seat 27. The face reaching from the seat 27 to the faceplate 22 is inclined as a groove for an arc welding to the connectionmember 30.

A raised portion 35 is arranged to the end portion of the connectionmember 30 which mounts on the seat 27. A height of the raised portion 35is similar to that of the raised portions 16, 26, 11 b and 32. A widthof the raised portion is similar to a sum-up width of the raisedportions 16 and 26.

The connection member 30 is arranged to aim to form the surfaces of theplate plates 11 and 21 being continuously just as. The central portionexcept for the both end portions of the connection member 30 is a plate31 and a plate thickness of the plate is substantially same to the platethickness of the face plates 11 and 21. An upper face of the raisedportion 35 a V-shape groove 36 is provided.

The groove 36 is arranged at a center of the width of the raised portion35. A width of the raised portion 35 is larger than a diameter of alarge diameter portion 252 of the rotary tool 250. The groove 36 becomesa subject matter for position detecting to lead the rotary tool 250.

The groove 36 is detected by a laser sensor and the axial center of therotary tool 250 is coincided with the groove 36. An extension line ofthe groove 36, namely on the axial center of the rotary tool 250, thereis the intersecting point of the two rib 23A and rib 23B.

The width of the connection member 30 is smaller than an interval of theface plates 11 and 21 of the two hollow frame members 10 and 20. Theconnection member 30 is made of the extruded frame member having thesame material of the hollow frame members 10 and 20. A length of theconnection member 30 is the same of the length of the hollow framemembers 10 and 20.

A distance P from the end portion of the face plate 11 to the endportion of the face plate 21 is the same pitch P of the truss structureof the other positions. A distance from the apex of the truss structureof the end portion of the hollow frame member 10 and the apex of thetruss structure of the end portion of the hollow frame member 20 is thesame pitch P of the truss structure of the other positions.

When the faces plates 11 and 12, 21 and 22 side is the apex, the trussstructure of the hollow frame member is an isosceles triangle. However,the truss structure of the end portion of the hollow frame members 10and 20 is not an isosceles triangle.

For the above stated reason, the rib 13A is connected to a midway of theface plate 12 and the rib 23A is connected to a midway of the face plate22. Between a connection portion between the rib 13A and the face plate12 and a connection portion between the rib 23A and the face plate 22, aspace for inserting the friction stir joining apparatus is formed.

The manufacturing method of this structure body will be explained. Thehollow frame members 10 and 20 are mounted on the bed 240. Next, theface plates 12 b and 22 b are abutted. Next, these frame members 10 and20 are fixed on the bed 240.

Next, the portions of the end faces 12 d and 22 d are fixed temporallyaccording to the arc welding manner. This temporary welding is carriedout intermittently.

An upper face of the bed 240 on which the abutted portion of the faceplates 12 b and 22 b are mounted is flat. Three portions which are thevicinity of the abutted portion of the face plates 12 b and 22 b, anintersecting point vicinity of the ribs 13A and 23A, and the face plates12 b and 22 b, and an intersecting point vicinity of the ribs 13B and23B and the face plates 12 and 22 are mounted on the bed 240 having thesame height.

With this condition, the rotary tool 250 of the friction stir joiningapparatus is inserted from the upper portion to the abutted portion ofthe raised portions 16 and 26 and is moved along to a joining line andthen the friction stir joining is carried out. The axial center of therotary tool 250 is a perpendicular direction (the direction along to thenormal line of the joining portion). However, against an advancingdirection of the rotary tool 250 the axial center is inclined as alreadyhave known.

The rotary tool 250 comprises the large diameter portion 252 and thesmall diameter portion 251 at a tip end of the large diameter portion252. The tip end (the lower end) of the small diameter portion 251 ofthe rotary tool 250 is positioned at a vicinity of a lower face from anupper face of the face plates 12 b and 22 b. The lower end of the largediameter portion 252 of the rotary tool 250 is positioned between theapex of the raised portions 16 and 26 and between the face plates 12 band 22 b of the inner side of the car of the railway vehicle (the faceside of the plates 11 and 21).

A diameter of the large diameter portion 252 of the rotary tool 250 issmaller than a width which is comprised of the two raised portions 16and 26. The small diameter portion 251 of the rotary tool 250 forms ascrew member.

During the friction stir joining, the apex face of the raised portions16 and 26 is pressed under a low portion a roller which moves the rotarytool 250 each other.

The raised portion 16 and 26 are detected by the laser sensor. Accordingto this, a height position of the raised portions 16 and 26 is requestedand an insertion amount of the rotary tool 250 is determined. Further, agap of the abutted portion of the two raised portions 16 and 26 isrequested and to this position the axial center of the rotary tool 250is coincided with.

According to this friction stir joining the gap of the abutted portionof the faceplate 12 b and 22 b is buried and joined. The originalmaterial of the metal for burying the gap is the raised portions 16 and22. The outer face side (the outer side of the car) of the face plates12 b and 22 b is joined flatly. To the outer face side of the faceplates 12 b and 22 b, no recessed portion of the joining line exists.

The upper face of the raised portions 16 and 26 becomes a convex formaccording to the large diameter portion 252 of the rotary tool 250. Atthe both ends of the recessed portion, the raised portions 16 and 26 areleft.

Next, the connection member 30 is mounted on the seats 17 and 27 of theface plates 11 and 21. One end (an end portion of the raised portion 32)of the connection member 30 is abutted an end portion of the plate 11 (aboundary between the raised portion 11 b and the seat 17).

Next, the end portion of the connection member 30 is fixed temporally tothe face plates 11 and 21 according to the arc welding manner. Thistemporary welding is carried out intermittently.

Next, using the friction stir joining apparatus which is used to thefriction stir joining of the abutted portion of the face plates 12 b and22 b the joining for one end of the connection member 30 and the endportion of the face plate 11 is carried out. This is same of the joiningof the abutted portion of the raised portions 16 and 26.

Next, the joining of the seat 27 and other end of the connection member30 is carried out. With a condition where the rotary tool 250 isinserted in to a portion to which the connection member 30 and the seat27 are overlapped, the rotary tool 250 is moved along to the joiningline and the friction stir joining is carried out. A width of the raisedportion 35 is larger than the diameter of the large diameter portion 252of the rotary tool 250.

At a center of the raised portion 35 the groove 36 is provided. Therotation axial center of the rotary tool 250 is coincided with thegroove 36. A tip end of the small diameter portion 251 of the rotarytool 250 is inserted deeply to the seats 17 and 27. With thisconstruction, the overlapping joining is carried out. The lower end ofthe large diameter portion 252 of the rotary tool 250 is positionedbetween the upper face of the connection member 30 being the non-raisedportion and the apex of the raised portion 35.

The upper face of the raised portion 35 become a recess form accordingto the large diameter portion 252 of the rotary tool 250. The upper faceof the raised portion 35 becomes a recess form according to the largediameter portion 252 of the rotary tool 250. At the both ends of therecessed portion the raised portion 35 is left.

The above stated sensor of the friction stir joining apparatus detectsthe groove 36 and along to the groove 36 the rotary tool 250 is moved.

FIG. 2 is schematic view showing a condition of the joining portion ofthe structure body after the joining. A hatching portion shows thejoining portion.

The axial center of the rotary tool 250 is positioned at the apex pointof the truss structure of the two ribs 13A 15 and 13B (23A and 23B) orthrough the perpendicular line of a vicinity thereof passes. Against theeccentric matter, it corresponds to an increase of the plate thicknessof the ribs 13A and 13B (23A and 23B), a shape of the arc for connectingthe rib and the face plate, a thickness of the connection member 20 30,and the thickness of the seats 17 and 27, etc. . .

When two rotary tools are used, the joining of the both ends of theconnection member 30 can be carried out at the same time.

According to the above stated construction, since one of the overlappingcoupling is made to the abutted coupling, according to an improvement ofthe coupling efficiency and a reduction of a stress concentration in abending portion, a strength can be improved.

Further, since the arc welding can be lessened, a thermal distortion ofthe structure body can be lessened, an appearance of the structure bodycan be improved, further an installation of an interior mountingmaterial can be carried easily.

According to the above stated construction, the joining of the bothfaces of the hollow frame members is carried out from one side face. Forthis reason, it is unnecessary to reverse the structure body to whichone face is joined. Accordingly, the structure body can be manufacturedat a low cost and with a high accuracy.

Further, the outer face of the joining portion of the face plates 12 band 22 b can be joined flatly. The raised portions 16, 26 and 35 arearranged in the inner side of the structure body and the inner side ofthe car but not existed at a portion (the outer face side, the outerside of the car) in which a flat face is required.

Further, at the outer side of the car no raised portion which causes bydeleting according to the rotary tool 250 exists. For this reason, thecut-off etc. of the raised portion is unnecessary and the car body canbe manufactured at a low cost.

Further, the bed 240 can be replaced by a backing member such as aroller etc. . .

Further, the abutted portion is joined at first, and next theoverlapping portion is joined. For this reasons, comparing the reversalcase, it is considered that the good friction stir joining can becarried out.

It is considered that the strength of the joining portion of theoverlapping portion (the joining portion of the seat 27 and theconnection member 30) and the strength of the strength of the bendingportion of the place plate 21 are inferior than the strength the abuttedportion (the joining portion of the face plate 11 and the connectionmember 30).

In this case, the end portion of the connection member 30 and the endportion of the face plate 21 are joined according to the arc weldingmanner. This arc welding can be carried out a portion necessary to havemore strength, for example only a position near to a window cornerportion.

Further, the member which is joined by the above stated manner can beused as an outer face (a face to be viewed by eye) of the structuremember such as a building structure.

The portion for mounting the connection member 30 can be set at thestructure and the portion in which it can bear to the load during thefriction stir joining. For example, the structure and the portion can beset as shown in FIG. 9 of the above stated document of Japaneseapplication patent laid-open publication No. Hei 9-309164 (EP 0797043A2).

A further embodiment of a structure body carried out a friction stirjoining according to the present invention shown in FIG. 5A and FIG. 5Bwill be explained. This is suited for a case in which by joining threeand more than three hollow frame members a large structure body ismanufactured. For example, the side structure body 201 is constituted bythe three frame members. The relationship between the hollow framemember 10 (for example, a first frame member) and the hollow framemember 20 (for example, a second frame member and a central framemember) at the left side and the connection member 30 is similar to theembodiment of the structure body shown in FIG. 1.

To another end (the right end) of the central hollow frame member 20(the second frame member) the left end of a hollow frame member 40 (forexample, a third frame member) and the connection member 30B are joined.The left end of the hollow frame member 40 (the third frame member) andthe connection member 30B are joined. The left end of the hollow framemember 40 (the third frame member) and the connection member 30B aresame to the left end of the central hollow frame member 20 (the secondframe member) and the connection member 30.

The structure of the another end (the right end) of the central hollowframe member 20 (the second frame member) is same the structure of theright end of the hollow frame member 10 (the first frame member). Thestructure of the left end of the hollow frame member 40 (the third framemember) which is joined to the right end of this hollow frame member 10(the first frame member) is same to the right end of the central hollowframe member 20 (the second frame member). The structure and thedirection of the connection member 30B are same to those of theconnection member 30.

The left end of the central hollow frame member 20 (the second framemember) and the hollow frame member 10 (the first frame member) areshown in FIG. 5A. The right end of the central hollow frame member 20(the second frame member) and the hollow frame member 40 (the thirdframe member) are shown in FIG. 5B. The left end of the central framemember 20 (the second frame member) shown in FIG. 5A extends to theright end of the central frame member 20 (the second frame member) shownin FIG. 5B, and an intermediate portion of the right end of the centralframe member 20 (the second frame member) is omitted.

The hollow frame member 40 (the third frame member) is comprised of twosheet face plates 41 and 42, truss structure arranged plural ribs 43Aand 43B and a seat 47. The face plate 42 has a projected plate 42 b anda raised portion 46 and the face plate 41 has a slope face 47 b.

Namely, when the three hollow frame members 10, 20 and 40 are carriedout to join, to one end (the left end) of the face plate 21 of thecentral hollow frame member 20 (the second frame member), a slope face27 b is provided, and to another end (the right end) of the face plate21 a raised portion (it corresponds to the raised portion 11 b) isprovided.

With this construction, all of the directions of the raised portion 32of the connection members 30 and 30B at the both ends of the centralhollow frame member 20 (the second frame member) direct in the leftportion.

As a result, since the directions of the raised portions 32 of theplural connection members 30 direct in the same direction, the erroneousarrangement of the connection members 30 can be lessened.

The joining procedure is that the three hollow frame members 10, 20 and40 are mounted on the bed 240 and restricted. Hereinafter is similar tothat of a case of FIG. 1.

The technical range according to the present invention is not limited tothe wordings stated on each claims of the “what is claimed is” item orthe wording stated on the “means for solving the problems”, however itcan refer to a range in which a person who belong to this field can beplaced easily:

According to the present invention, without of regard of the dimensionaccuracy of the hollow frame member and the like, the good joining fromone side face of the hollow frame member can be carried out.

What is claimed is:
 1. A structure body comprising: two hollow frame members which are joined; each of said two hollow frame members includes two face plates, and between said two face plates and connected thereto are plural ribs; and a first end portion of one of said two face plates projects beyond a second end portion, of the other of said two face plates of each hollow frame member; the first, projected end portions of the face plates of the two hollow frame members are joined together by a friction stir welding; a connection member is provided between the second end portions, of the other of the two face plates of the two hollow frame members, and respective end portions of the connection member are joined by friction stir welding to a connection portion of the second end portion of the other of said two face plates, of one of said two hollow frame members, and to a connection portion of the second end portion of the other of said two face plates of the other of said two hollow frame members and said ribs; said friction stir welding between said one of said two hollow frame members and one end portion of said connection member is at an abutted portion of said one of said two hollow frame members and said connection member; and said friction stir welding between the other of said two hollow frame members and the other end portion or said connection member is at an overlapping portion of said frame and said connection member.
 2. A structure body according to claim 1, wherein the other of the two hollow frame members and the other end of the connection member are welded with a joining portion of the other of said two hollow frame members and the other end of said connection member arranged adjacent each other.
 3. A structure body comprising: a first hollow frame member, a second hollow frame member, and a third hollow frame member which are joined; each of the three hollow frame members includes two face plates, and between said two face plates and connected thereto are plural ribs; and a first end portion of one of said two face plates projects beyond a second end portion, of the other of said two face plates of each hollow frame member; the second end portion of the other of said two face plates of said first hollow frame member and the second end portion of the other of said two face plates of said second hollow frame member are joined through a first connection member; the other second end portion of the other of said two face plates of said second hollow frame member and the other end portion of the other of said two face plates of said third hollow frame member are joined through a second connection member; the respective joinings of said connection members with the second end portions are friction stir weldings; said friction stir weldings between said first hollow frame member and said first connection member and said friction stir welding between said second hollow frame member and said second connection member are abutting joinings; and said friction stir welding between said second hollow frame member and said first connection member and said friction stir welding between said third hollow frame member and said second connection member are an overlapping joining.
 4. A hollow frame member, comprising: two face plates; plural ribs, said plural ribs being connected between said two face plates; an end portion of one of said two face plates being projected beyond an end portion of another of two face plates; at said end portion of said one of said two face plates, a raised portion is provided; a recessed portion is opened at a side of said end portion of the other of said two face plates; said recessed portion and an outer face of the other of said two face plates are connected through a slope face; and said end portion of said one of said two face plates and said recessed portion are adapted to be subjected to friction stir welding.
 5. A hollow frame member according to claim 4, further comprising a connection portion at said end portion of the other of said two face plates, said recessed portion being provided at said connection portion.
 6. A hollow frame member according to claim 5, wherein said connection portion is a portion where ribs, of said plural ribs, are connected at said other of said two face plates.
 7. A hollow frame member according to claim 6, wherein said ribs connected at said connection portion include a rib, of the plural ribs, extending closest to said end portion of the one of said two face plates. 